After my Xperia Z3's screen was damaged I had to send it to repairs (an independendent repair provider). I was unable to log out of any accounts and while the phone was away, I noticed that my facebook messages were being read, so I logged out all device remotely by changing the password. When my phone returned however, it had tons of unread notifications - and the clock had been changed. Did the repair service change the time so I wouldn't see that they read my notifications/does changing the time make read notifications go unread again? How can I tell if they have been going through my messages and other data?
Simple, you put a password on it. Or.. Or next time you want to take it in for repair. Use Titanium backup. Backup all the apps and data. Store it to the sd card. Wipe phone completely, take out sd card, send it in for repairs. And no changing the time wont do much.